Technical Field
The present invention relates to a shovel that includes an excavation attachment moved by a hydraulic cylinder, and to a method of controlling the shovel.
Description of Related Art
An overload prevention device for hydraulic power shovels has been known.
This overload prevention device prevents, during excavation work of a power shovel, a lift of front wheels by detecting a reaction force from the ground as a holding hydraulic pressure in the head-side oil chamber of a boom cylinder and opening a relief valve when the holding hydraulic pressure reaches a predetermined pressure.
Furthermore, the lift of front wheels is prevented by automatically causing a boom, an arm and a bucket to operate by putting a boom main operation valve, an arm main operation valve, and a bucket main operation valve into operation, instead of opening the relief valve.